An engine's acceleration profile may be analyzed or characterized. In some instances, such an analysis may be used to generally operate the engine in a low or idle state or mode of operation to obtain enhanced fuel efficiency. For example, in connection with turboshaft jet engines, an analysis may be performed to provide for an improved or enhanced specific fuel consumption (SFC), potentially at the expense of surge margin.
An engine manufacturer may choose to reduce surge margin to compensate for power loss. For example, when a starter generator is installed on a compressor of an engine, shaft power losses may reduce the engine's response to rotor load changes. Strict load limits (e.g., electrical load limits) may need to be established and adhered to in order to prevent electrical overloads. An approach to providing necessary engine starting torque while ensuring that electrical generating limits are not exceeded is to design a custom starter generator for the particular engine. In some instances, it might be difficult or undesirable to develop a custom starter generator.